膜下滴灌水稻基因型耐缺铁性评价

【目的】新疆生产建设兵团采用膜下滴灌技术后,水稻缺铁黄化现象较为严重,研究该条件下水稻对缺铁反应的基因型差异,可为耐缺铁性水稻基因型的筛选和分类提供可靠的理论依据。 【方法】以六个水稻基因型为研究材料,采用膜下滴灌技术管理。在水稻幼苗期、分蘖期和成熟期随机采样,测定不同基因型水稻的分蘖数、生物量、产量以及铁含量,利用隶属函数分析和聚类分析研究了水稻在全生育期对缺铁胁迫反应的基因型差异。 【结果】水稻在幼苗期、分蘖期和成熟期对缺铁的反应存在基因型差异。在幼苗期水稻基因型 T-04 和 T-05 的叶片活性铁含量显著低于其他基因型;T-201 在幼苗期叶片活性铁、地上部铁的分配,分蘖期叶片铁含量和地上部干物质均较高;在分蘖期 T-04 铁的转移能力最小,但是 T-04 的分蘖数较高;在成熟期 T-04 的有效分蘖与其他基因型差异不显著,T-04 的产量处于中等水平,但是其籽粒铁的收获指数低于其他基因型水稻。聚类分析显示耐缺铁水稻基因型 T-43 的各指标高于其他基因型。 【结论】在水稻的幼苗期和分蘖期叶片铁的有效利用和自身铁的转移保证了水稻的生长和较高有效穗数,根据全生育期水稻铁营养效率和产量的基因型差异初步确定 T-43 耐缺铁能力较强,T-04 为对缺铁敏感的水稻基因型。     

Growth and Iron Uptake of Lowland and Aerobic Rice Genotypes under Flooded and Aerobic Cultivation

With increasing water shortages in China, rice (Oryza sativa L.) cultivation is gradually shifting away from continuously flooded conditions to partly or even completely aerobic conditions. The effects of this shift on the growth and iron (Fe) nutrition of different aerobic and lowland rice genotypes are poorly understood. A field experiment was conducted to determine the effects of cultivation system (aerobic vs. flooded), genotype (five aerobic rice varieties and one lowland rice variety), and Fe fertilization [no Fe and 30 kg ha^?1 ferrous sulfate (FeSO₄·7H₂O] on rice grain yield and Fe nutrition. Plants were sampled at tillering and physiological maturity. In both aerobic and flooded plots, Fe application significantly increased shoot dry weight, shoot Fe concentration, and shoot Fe content at tillering but not physiological maturity. At physiological maturity, grain yield and Fe and grain harvest indices were significantly lower in aerobic than in flooded plots. Shoot dry weight and shoot Fe content differed among genotypes at tillering and at physiological maturity. The grain harvest index of aerobic rice genotype 89B-271-17(hun) was significantly greater than that of the other five genotypes when no Fe was applied. Because soil Fe fertilization did not improve the Fe nutrition of rice in aerobic plots, the results indicate that the shift from flooded to aerobic cultivation will increase Fe deficiency in rice and will increase the problem of Fe deficiency in humans who depend on rice for nutrition.     

Effect of sulphur in the prevention of incipient iron chlorosis in corn

Abstract

Results of a field experiment, comprising elemental S and three commercial preparations of Fe, applied with and without several other factors showed that the application of S was significantly better than that of Fe supplying materials in preventing the incipient chlorosis of corn leaves on the alkaline calcareous soils. Prevention of chlorosis in corn due to sulphur application increased the grain yield of corn 25–31%.

Leaf samples from plants raised with Fe supplying materials were chlorotic even though they contained significantly higher amounts of Fe. Persistence of chlorosis in spite of high Fe content of leaves, vis a vis freedom from chlorosis in spite of low Fe content, suggest that deficiency of Fe was not a factor in chlorosis. Freedom from chlorosis accompanied by significant increases in corn yields due to S application, on the contrary, show that it was the lack of S rather than Fe as the cause of Chlorosis.

When the supply of S is low, Fe seems to be subjected to a great deal of chemical inactivation and under conditions of stress more and more absorption of Fe is necessitated. In all probability the rate of inactivation exceeds the rate of absorption and chlorosis develops. In this situation either the plant's ability to utilize iron is affected or the physiological availability of absorbed iron is very low. Increased S seems to arrest the process of Fe inactivation by providing a better nutritional environment.     

Physiological investigations of management and genotype options for adapting rice production to iron toxicity in Madagascar

Iron (Fe) toxicity is one of the major mineral disorders affecting rice (Oryza sativa L.) production in Madagascar. This study aimed at linking physiological and agronomic responses of diverse rice genotypes to Fe resistance mechanisms with different nutrient management practices. Twenty‐three local and exotic rice varieties were grown in Fe‐toxic soil in parallel greenhouse and field experiments and subjected to two treatments: (1) no fertilizer; (2) mineral and organic fertilizer application at recommended rates. Growth, straw and grain yield, symptom formation, and physiological responses including Fe uptake, root plaque formation, and lipid peroxidation were monitored. The application of fertilizer significantly decreased average shoot Fe concentrations partly due to Fe exclusion favored by enhanced root plaque formation. Visual symptoms negatively correlated with straw biomass in both experiments and grain yield in the greenhouse experiment, and positively correlated with lipid peroxidation. However, no plausible correlation occurred with grain yield in the field due to sterility in exotic varieties un‐adapted to local climate. Even though grain Fe concentrations were orders of magnitude lower than in vegetative tissue, some exotic varieties were significantly superior to local checks. Our results provide insight into management and genotype options for adapting rice to Fe toxicity under field conditions.     

Physiological basis of iron chlorosis tolerance in rice (Oryza sativa) in relation to the root exudation capacity

Micronutrient deficiency in cultivable soil, particularly that of iron (Fe) and zinc (Zn), is a major productivity constraint in the world. Low Fe availability due to the low solubility of the oxidized ferric forms is a challenge. An experiment was, thus, executed to assess the performance of eight genetically diverse rice genotypes on Fe-sufficient (100 µM) and Fe-deficient (1 µM) nutrient solution, and their ability to recover from Fe deficiency was measured. Fe efficiency under Fe deficiency in terms of biomass production showed a significant positive correlation with the root release of phytosiderophore (PS) (R² = 0.62*). This study shows that the Fe deficiency tolerance of Pusa 33 was related to both a high release of PS by the root and an efficient translocation of Fe from the root to the shoot as the Fe–PS complex, which could be useful for improving the Fe nutrition of rice particularly under aerobic conditions.     

Effect of iron deficiency on the growth,development and grain yield of some selected upland rice genotypes in the rainforest

Abstract

Iron deficiency is a major production constraint of upland rice in the tropics despite is abundance in the soil. This investigation aimed to explicate the effect of iron deficiency on the growth, development, grain yield and its attributes of some selected upland rice in the rainforest. Field experiments were established at Africa Rice sub-Station, Ibadan, Nigeria. The treatments consisted of 35 upland rice genotypes and availability of iron in the soil (Fe-sufficient and Fe-deficient). The treatments were arranged in alpha lattice design with three replications. It was observed that upland rice sown in iron (Fe) deficient soils had significantly lower growth (plant height, number of tillers and seedling vigor), flowered later, with significantly lower yield attributes (1000 grain weight, filled grain) and grain yield than those sown in Fe-sufficient soils. Conversely, the number of unfilled grains were significantly higher in upland rice sown in Fe-deficient than those in sufficient soils. Percentage yield loss was in the range 98.00% to 22.95% for China best and Faro 65 respectively. Genotypes were identified to be tolerant (Faro 65, NERICA 3 and IRAT 109) and susceptible (Ofada 2, NERICA 5 and China Best) to Fe-deficiency based on their percentage grain yield loss. These evidences suggested that despite the increased phenology of upland rice sown in Fe-deficient soils their reproductive growth was suppressed through increased number of unfilled grains as witnessed in China Best and Faro 64.     

Evaluating grain sorghum hybrids for tolerance to iron chlorosis

Grain sorghum production in calcareous soils is frequently affected by iron (Fe) chlorosis. Greenhouse experiments were conducted to screen sorghum hybrids for their tolerance to iron deficiency chlorosis (IDC) and evaluate the effectiveness of Fe chelate application in alleviating IDC. Treatments in Exp. 1 were a factorial combination of 14 sorghum hybrids and three Fe chelate application rates (0, 3.4 and 6.8?kg product ha^?1) applied in-furrow with the seed at the time of planting. Exp. 2 evaluated two sorghum hybrids (85Y40 and NK5418) and three Fe chelate rates (0 and 3.4?kg product ha^?1) at planting, and a split treatment of 3.4?kg ha^?1. Results showed iron chelate application suppressed IDC and increased leaf chlorophyll content and grain yield in susceptible hybrids. Split application of Fe chelate suppressed IDC and increased grain yield. Our results indicate sorghum hybrids G8G08, 86G32 and 87P06 showed promise for tolerance to IDC.     

Agronomic evaluation of mulching and iron nutrition on productivity,nutrient uptake,iron use efficiency and economics of aerobic rice-wheat cropping system

Field experiments were carried out during rainy (kharif) and winter (rabi) seasons (June–April) of 2008–2010 at Indian Agricultural Research Institute (IARI), New Delhi, to study the productivity, nutrients uptake, iron (Fe) use-efficiency and economics of aerobic rice-wheat cropping system as influenced by mulching and Fe nutrition. The highest yield attributes, grain and straw yields (5.41 tonnes ha^?1 and 6.56 tonnes ha^?1, respectively) and nutrient uptake in rice was recorded with transplanted and puddled rice (TPR) followed by aerobic rice with Sesbania aculeata mulch. However, residual effect of aerobic rice with wheat straw mulch was more pronounced on yield attributes, grain and straw yields (4.20 and 6.70 tonnes ha^?1, respectively) and nutrient uptake in succeeding wheat and remained at par with aerobic rice with Sesbania mulch. Application of iron sulfate (FeSO₄) at 50 kg ha^?1 + 2 foliar sprays of 2% FeSO₄ was found to be the best in terms of all the yield attributes, grain and straw yield (5.09 and 6.17 tonnes ha^?1, respectively) and nutrient uptake and remained at par with 3 foliar sprays of 2% FeSO₄. Although residual effect of iron application failed to increase the yield attributes, yield and nutrient uptake nitrogen, phosphorus and potassium (N, P, K) except Fe. The highest system productivity, nutrient uptake, gross returns, net returns, B: C ratio and lowest cost of cultivation were recorded with aerobic rice with wheat straw and Sesbania aculeata mulch. Application of FeSO₄ at 50 kg ha^?1 + two foliar sprays of 2% FeSO₄ was found better in respect of system productivity, nutrient uptake, gross returns, net returns, B:C ratio and cost of cultivation in aerobic rice-wheat cropping system. The Fe use efficiency values viz. partial factor productivity (kg grain kg^?1 Fe), agronomic efficiency (kg grain increased kg^?1 Fe applied), agrophysiological efficiency (kg grain kg^?1 Fe uptake), physiological efficiency (kg biomass kg^?1 Fe uptake), apparent recovery (%) utilization efficiency and harvest index (%) of applied Fe were significantly affected due to methods of rice production and various Fe nutrition treatments in aerobic rice and aerobic rice-wheat cropping system.     

Phytosiderophore release as a criterion for genotypic evaluation of iron efficiency in oat

Iron (Fe) deficiency in small grains grown on calcareous soils results in reduced yields, is difficult and expensive to treat with fertilizer, and is complicated to overcome by genetic field screening due to heterogeneous soil and environmental conditions. Recently, phytosiderophore release has been linked to ability of species and genotypes to resist Fe‐deficiency chlorosis. We propose a laboratory technique to measure phytosiderophore release by Fe‐deficient oat (Avena sativa L.) genotypes as a selection method for Fe‐deficiency chlorosis resistance in oat. Plants were grown in Fe‐limiting nutrient solution and phytosiderophore release was measured on 11 days. Summations of daily phytosiderophore release by 17 oat genotypes correlate well with Fe‐deficiency chlorosis scores in the field (r = ‐0.70, p = 0.01). The proposed method consistently identified the genotypes most susceptible to Fe deficiency but did not clearly separate the moderately susceptible genotypes. In these latter genotypes, other factors such as active uptake sites, root growth rate, utilization of acquired Fe, or soil interactions may be modifying factors to phytosiderophore in Fe efficiency. Quantification of phytosiderophore provides a useful selection criterion for oat by eliminating the most inefficient types and with refinement, may become a powerful tool for identifying Fe efficiency in grass crops.     

Copper induced iron deficiency in wheat (Triticum aestivum L)

Abstract

A pot experiment was conducted to study the interaction effects of phosphorus and copper on wheat. The soils used were calcareous loamy sand (ls) and non calcareous sandy loam (sl). Four levels of Cu (0, 5, 10 and 20?mg Cu kg^?1 soil) and six levels of P (0, 25, 50, 100, 200 and 400?mg P kg^?1 soil) were applied in all possible combinations with three replications. Soil pH decreased with Cu application while Olsen P increased with P application in both soils. Growth and yield of wheat improved significantly with graded levels of applied P. However, when any level of P was combined with 20?mg Cu kg^?1 soil, severe iron chlorosis of leaves, a drastic reduction in growth and chlorophyll content was observed in calcareous ls only. The results indicated that it was Cu and not P that induced Fe deficiency in wheat grown in alkaline calcareous soil and the Cu requirement of the crop seemed to be much lower in the calcareous ls. Root dry matter, grain and straw yield decreased with increasing levels of applied Cu in ls but in sl maximum increase of 62.5, 74.3 and 63.7 per cent in root, grain and straw yield was observed with a combined application of 400?mg P and 5?mg Cu kg^?1 soil over control. Accumulation of Cu in roots decreased the Fe absorption by roots which indicated that Fe chlorosis of wheat leaves is expected when Cu: Fe concentration ratio in root is > 0.30.     

Effects of exogenous SA supplied with different approaches on growth,chlorophyll content and antioxidant enzymes of peanut growing on calcareous soil

To assess the role of salicylic acid (SA) supplied with 5 approaches in alleviating chlorosis induced by iron (Fe) deficiency in peanut plants growing on calcareous soil, SA was supplied as soil incorporation, making slow-release particles, seed soaking, irrigation and foliar application. SA application, particularly, SA supplied by slow release particles, dramatically increased growth parameters, yield and quality of peanut, and increased Fe concentration in peanut grain. Meanwhile, SA application increased the H⁺-ATPase activity, reduced pH of soil, increased Fe³⁺-Chelate Reductase (FCR) activity in roots, and increased Fe concentration in roots. Furthermore, SA increased active Fe content and increased chlorophyll content. In addition, SA improved enzymes activities containing superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and protected Fe deficiency induced oxidative stress. Therefore, SA has a good effect on alleviating chlorosis induced by Fe deficiency on calcareous soil. However, in the 5 SA supplied approaches, foliar application and making slow release particles were more effective.     

Classification of rice genotypes based on their mechanisms of adaptation to iron toxicity

Iron (Fe) toxicity is a nutritional disorder that affects lowland rice (Oryza sativa L.). The occurrence of excessive amounts of reduced Fe(II) in the soil solution, its uptake by the rice roots, and its transpiration‐driven transport result in elevated Fe(II) concentrations in leaf cells that catalyze the formation of reactive oxygen species. The oxidative stress causes rusty brown spots on leaves (bronzing) and the reduction of biomass and yield. While the use of resistant genotypes is the most promising approach to address the problem, the stress appears to differentially affect rice plants as a function of plant age, climatic conditions, stress intensity and duration, and the prevailing adaptation mechanism. We comparatively assessed 21 contrasting 6‐week‐old rice genotypes regarding their response (symptom score, biomass, Fe concentrations and uptake) to a 6 d iron pulse of 1500 mg L^–1 Fe(II). Eight selected genotypes were further compared at different stress intensities (0, 500, 1000, and 1500 mg L^–1 Fe(II)) and at different developmental stages (4‐, 6‐, and 8‐week‐old plants). Based on Fe‐induced biomass reduction and leaf‐bronzing score, the tested spectrum was grouped in resistant and sensitive genotypes. Linking bronzing scores to leaf iron concentrations allowed further differentiation into includer and excluder types. Iron precipitation on roots and organ‐specific iron partitioning permitted to classify the adaptation strategies into root exclusion, stem and leaf sheath retention, and leaf blade tissue tolerance. The effectiveness of these strategies differed with stress intensity and developmental stage. The reported findings improve the understanding of Fe‐stress response and provide a basis for future genotype selection or breeding for enhancing Fe‐toxicity resistance in rice.     

Interactive effects of salinity and iron deficiency on different rice genotypes

Salinity adversely affects plant growth, photosynthesis, and availability of nutrients including iron. Rice (Oryza sativa L.) is susceptible to soil salinity and highly prone to iron (Fe) deficiency due to lower release of Fe‐chelating compounds under saline conditions. In order to investigate the effects of salinity and low iron supply on growth, photosynthesis, and ionic composition of five rice genotypes (KS‐282, Basmati Pak, Shaheen Basmati, KSK‐434 and 99417), a solution culture experiment was conducted with four treatments (control, 50 mM NaCl, Fe‐deficient, and 50 mM NaCl + Fe‐deficient). Salinity and Fe deficiency reduced shoot and root growth, photosynthetic and transpiration rates, chlorophyll concentration, and stomatal conductance. The reduction in all these parameters was more in the interactive treatment of salinity and low Fe supply. Moreover, a significant increase in shoot and root Na⁺ with corresponding decrease in K⁺ and Fe concentrations was also observed in the combined salinity and Fe‐deficiency treatment. Among the tested genotypes, Basmati Pak was the most sensitive genotype both under salt stress and Fe deficiency. The genotype KS‐282 performed better than other genotypes under salinity stress alone, whereas Shaheen Basmati was the best genotype under Fe deficiency in terms of all the studied parameters.     

花生缺铁黄化的敏感时期及耐低铁品种的筛选指标

采用盆栽试验,系统研究了石灰性土壤上16个花生品种在各个生育时期新叶的黄化度、叶绿素值、活性铁含量的差异及其动态变化。结果表明,缺铁胁迫下花生耐低铁和铁敏感品种间叶片的黄化程度存在着显著差异,大多数铁敏感品种在出苗后50～65 d时黄化度最高。供试16个品种顶部新展开叶片的叶绿素值（SPAD值）和活性铁含量在整个生育期的变幅分别为4.5～34.6和8.0～36.3 mg/kg, FW,随生长时间的延长两者均呈高―低―高的动态变化趋势。在生长前期,耐低铁品种新叶的叶绿素值和活性铁含量均显著高于铁敏感品种;开花期是花生对缺铁胁迫最为敏感的时期,此阶段黄化现象最严重、各品种新叶的叶绿素值和活性铁含量最低。相关分析表明,在生长前期叶绿素值与黄化度、活性铁及荚果产量之间均呈极显著的相关关系。新叶叶绿素值可作为花生耐低铁品种筛选的一可靠指标。     

Activities of Iron‐Containing Enzymes in Leaves of Two Tomato Genotypes Differing in Their Resistance to Fe Chlorosis

Abstract

Two tomato (Lycopersicon esculentum Mill., cvs. Pakmor and Target) genotypes differing in resistance to iron (Fe) deficiency were grown in nutrient solution under controlled environmental conditions over 50 days to study the relationships between severity of leaf chlorosis, total concentration of Fe, and activities of Fe‐containing enzymes in leaves. The activities of Fe‐containing enzymes ascorbate peroxidase, catalase, and guaiacol peroxidase, and additionaly the activity of glutathione reductase, an enzyme that does not contain Fe, were measured. Plants were supplied with 2 × 10^?7 M (Fe deficient) and 10^?4 M (Fe sufficient) FeEDTA, respectively. Leaf chlorosis appeared more rapidly and severely in Target (Fe deficiency senstive genotype) than Pakmor (Fe deficiency resistant genotype). On day 50, Pakmor had 2‐fold more chlorophyll than Target under Fe deficiency, while at adequate supply of Fe the two genotypes were very similar in chlorophyll concentration. Despite distinct differences in development of leaf chlorosis and chlorophyll concentrations, Pakmor and Target were very similar in concentrations of total Fe under Fe deficiency. In contrast to Fe concentration, activities of Fe‐containing enzymes were closely related to the severity of leaf chlorosis. The Fe‐containing enzymes studied, especially catalase, showed a close relationship with the concentration of chlorophyll and thus differential sensitivity of tomato genotypes to Fe deficiency. Glutathione reductase did not show relationship between Fe deficiency chlorosis and enzyme activity. The results confirm that measurement of Fe‐containing enzymes in leaves is more reliable than the total concentration of Fe for characterization of Fe nutritional status of plants and for assessing genotypical differences in resistance to Fe deficiency. It appears that Fe deficiency‐resistant genotype contains more physiologically available Fe in tissues than the genotype with high sensitivity to Fe deficiency.     

华南地区不同品系水稻积累砷特征及其影响因素

选用华南地区较为常见的杂交稻、优质常规稻2个水稻品系,16个水稻品种,通过土壤盆栽试验,待其成熟收获后,分析水稻根表、根部、秸秆、糙米中砷含量及相关影响元素的含量,旨在研究不同水稻品系（种）对砷吸收、转运和积累规律以及其影响因素,为低积累、高耐性水稻品系（品种）的选择及相应的农业措施提供科学的理论依据。结果表明,砷在水稻中的分布情况为根表〉根部〉秸秆〉糙米;供试的糙米中砷含量为0.18~0.47mg.kg-1,均符合国家卫生标准（GB4810—1994）。水稻根表铁锰膜中砷含量随根表中铁、锰的增加而富集,相关分析表明,根表铁锰膜形成可以有效降低糙米砷积累,而秸秆磷可以有效降低秸秆中砷的积累。杂交稻各部位的砷含量及转移系数均高于常规稻,且秸秆和糙米砷含量差异达到显著水平;天优122的糙米砷积累能力高于其他品种,美香占2号低于其他品种。     

Effect of polyolefin resin coated slow release iron fertilizer and its methods of application on rice production in calcareous soil

Experiment was carried out to evaluate the, efficiency of different iron sources including polyolefin resin coated slow release Fe fertilizer (PRCCFe) and its methods of application on the performance of rice var. Swarna during rainy seasons of 2001 and 2002 under calcareous soil at Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The pots were filled with 10 kg calcareous soil having high CaCO₃ (36.32%) and low iron contents (1.45 pp—less than critical limit). The experimental treatments comprised five iron sources (NPK + 100% pyrite, NPK + 100% polyolefin resin coated slow release Fe (PRCSRFe), NPK + 50% pyrite + 50% PRCSRFe, NPK + 75% pyrite + 25% PCRSRFe, and NPK + 25% pyrite + 75% PCRSRFe and two methods of application (uniform and co-situs) including one control (NPK only). These 11 treatment combinations were laid out in Completely Randomized Block Design (CRBD) replicated thrice. The two methods of iron application did not differ significantly with respect to crop yield though higher yield was recorded with co-situs application. Among the Fe sources, application of iron 75% through to + 25% through polyolefin resin coated slow release Fe fertilizer produced the highest grain yield.     

Ratios of Nutrients in Lowland Rice Grown on Two Iron Toxic Soils in Nigeria

ABSTRACT

Iron (Fe) toxicity is a widespread nutritional soil constraint affecting rice production in the wetland soils of West Africa. Critical levels of total iron in plant causing toxicity is difficult to determine as different rice cultivars respond to excessive Fe^{2 +} in various ways in what is called “bronzing” or “yellowing” symptoms (VBS). An investigation was conducted to evaluate the relationship between plant growth and nutrient ratios at four iron levels (1000, 3000, 4000 μ g L^?1) and control. This involved two rice cultivars (‘ITA 212’ and ‘Suakoko 8’), and two soil types (Aeric Fluvaquent and Aeric Tropaquept). The experimental design was a 2 × 2 × 4 factorial in a completely randomized fashion with four replications. The results showed that nutrient ratios [phosphorus (P)/Fe, potassium (K)/Fe, calcium (Ca)/Fe, magnesium (Mg)/Fe, and manganese (Mn)/Fe), Fe content, and Fe uptake vary widely with the iron levels as well as with the age of the cultivars. The iron toxicity scores expressed as VBS increased with increasing Fe^{2 +} in the soils, resulting in simultaneous reduction of the following variables: plant height, tiller numbers/pot, relationships grain yield (GY) and dry matter yield (DMY). There were no significant difference between nutrient ratios, Fe contents, Fe uptake, the GY and DMY of both rice cultivars on both soil types. Multiple stepwise regression analysis showed that Fe uptake and Fe contents contributed 42% and 17% respectively to the variation in the grain yield of ‘ITA 212’ on Aeric Tropaquept. On both soil types and cultivars, Fe uptake and Fe content contributed between 26 and 68% to the variation in the DMY, while the nutrient ratios (P/Fe, K/Fe, Ca/Fe, and Mn/Fe) contributed between 3% and 13% DMY. Thus, it could be concluded that iron toxicity in rice is more a function of a single nutrient (Fe) rather than nutrient ratios.     

Phytic acid,iron and zinc content in wheat ploidy levels and amphiploids: the impact of genotype and planting seasons

Micronutrient deficiency is one of the most common and widespread nutritional issues. Among the factors mitigating the bioavailability of Zn (zinc) and Fe (iron), phytic acid plays a key role; therefore, in order to scrutinize genetic alterations ?related to micronutrient and phytate contents, we examined the concentrations of zinc, iron, and phytic acid, as well as its mole ratio to ?zinc in various wheat species grown in two planting seasons. The concentrations of phytic acid and its mole ratio to zinc were 0.61?1.55 g kg^?1 dry weight and 1.88?4.17 for autumn, and 0.97?2.02 g kg^?1 dry weight and 2.10?4.05 for spring planting. There was a significant discrepancy among wheat species; tritipyrum had the highest concentration of iron, phytic acid and its mole ratio to zinc, and T. monococcum and T. aestivum recorded reasonable zinc bioavailability. Correlation studies between grain phytic acid concentrations and other measured traits revealed various relationships, denoting an irrefutable impact of planting season and wheat ploidy levels on modification of wheat genotypes. The characters contributing more positively with principal component (PC) 1 were Zn and Fe under spring planting and Fe under autumn planting. Spike number per square meter, biological yield and grain yield in spring cultivation, and grain zinc concentration in autumn cultivation were positively correlated to principal component (PC) 2. Given that the concentration of Fe and Zn in all the studied genotypes is relatively high and due to the existence of other desirable agronomic traits, this study believes that it could possibly enhance the applicability of some of these genotypes for breeding purposes.     

Alien cytoplasm effects on phytosiderophore release in two spring wheats (Triticum aestivum L.)

Iron (Fe) deficiency is a difficult nutrient problem particularly in crop plants grown on calcareous soils. Recently, phytosiderophore (PS) release has been linked to the ability of graminaceous species and genotypes to withstand Fe-deficiency chlorosis. So enhancing PS release is a critical step to improve iron efficiency of plants grown on iron stressed soils. The effects of alien cytoplasm on PS release in spring wheat were studied by analyzing PS release from twenty wheat genotypes, including two spring wheat 881 and 352-35, and their 18 alloplasmic lines with the participation of cytoplasms from the Aegilops and Triticum species. Different genotypes were grown in iron sufficient and deficient nutrient solution under controlled environmental conditions. PS release rates were determined at two or three days intervals after onset of iron deficiency symptoms by the measurement of iron mobilizing capacity of root exudates from freshly precipitated Fe^III hydroxide. High amounts of phytosiderophores were released from roots of all wheat genotypes without iron supplied, and the amount progressively increased with the development of iron deficiency chlorosis. The results revealed that (1) the release rate of phytosiderophores from roots of common wheat could be considerably influenced by alien cytoplasms. Some alien cytoplasms exerted positive effects, some ones did negative effects, and the other ones had no significant effects. (2) the same alien cytoplasm could affect similarly or oppositely the phytosiderophores release from different wheat. (3) some alien cytoplasms, such as Chinese Spring, Ae. speltoides Tausch and Ae. cylindrica Host showed promising and potential in improving the rate of phytosiderophore release in common wheat. These cytoplasms which showed the desired effect should be given priority in interspecific and intergeneric hybridization to develop and reconstruct the needed wheat cultivars.